Brain death usually occurs within five to 10 minutes of cessation of blood to the brain seen in cardiac arrest, circulatory arrest, shock, exsanguination, cerebrovascular accidents (CVA's or strokes), or other cause of ischemia or anoxia to the brain. An approach to forestall the results of ischemia or anoxia to the brain will allow the treating physician to have more time to save the life of the patient. Specifically, if an approach to sparing the neurons (cell bodies of the functional brain or grey matter) of the central nervous system (CNS) immediately and over a rapid time interval, the white matter (axons), then the physician can more readily save the patient with circulatory arrest or other causes of brain ischemia. In effect, it is desirable to have a state of suspended animation in which the brain will have little damage due to ischemia or anoxia.
Trauma to the brain and/or spinal cord may result in direct injury to the central nervous system (CNS) tissue as well as to swelling or edema of this tissue against the walls of the skull or spinal canal. In the case of hemorrhage, there may be compression of the brain or spinal cord from within or around the tissue. After a period of time (minutes to hours to days), death of the tissue may occur causing irreversible damage.
Pathology to the brain may occur due to blunt injuries, such as a blow to the head, resulting in hemorrhage within or around the brain and associated swelling of brain tissue. Stroke, tumor, or other intracranial disease may also cause hemorrhage or swelling of brain tissue. Diagnosis of these diseases is made after careful neurological examination that is confirmed by imaging procedures including M.R.I., C.T., and ultrasound studies of the brain. Unfortunately, it is often difficult to control injury to the brain using conventional neurosurgical means including medical and surgical intervention.
Spinal injury may occur in blunt trauma due to a direct blow or to coup-countercoup injury. There may be direct pressure placed on the spinal cord as a result of a fractured or dislocated vertebral body (-ies) or disc, resulting in sensory and motor deficits below the level of the lesion. The mechanism of spinal injury is often related to swelling of the tissues of the spinal cord. Immediate treatment must be administered to prevent or diminish the effects of spinal cord compression and tissue edema.
Spinal cord ischemia may also occur during or following surgery on the aorta, including abdominal aneurysm repair with a prosthetic graft. Motor, sensory, and autonomic functions may be severely compromised or lost if the spinal cord is made ischemic. In the case where brain cooling can result in an extended period of resuscitation, spinal cord ischemia may occur. Therefore, hypothermia of the brain in resuscitation should be accompanied with hypothermia of the spinal cord.
Current treatment for swelling of the brain or spinal cord is not always satisfactory. In the severely injured brain or spinal cord, medical therapy to control swelling is usually applied systemically resulting in high levels of medication in the rest of the body with very low concentrations reaching the brain or spinal cord. Surgical intervention to decompress the brain or spinal cord requires major intervention through opening the skull or spinal column to expose the area and prevent compression against the fixed volume of the bony walls. Ventriculostomy (placing a tube into the lateral ventricle of the brain) is usually not performed acutely, and by the time it is used in the sub-acute phase, there may already be permanent damage to the brain.
Hypothermia has proved encouraging in the recent literature for the purpose of decreasing oxygen consumption and for decreasing swelling of CNS tissue. Unfortunately, cooling of the entire body to cool the brain or spinal cord does have inherent dangers. The heart responds to hypothermia with arrhythmias, and the blood clotting mechanisms may be severely impaired resulting in hemorrhage. Moreover, cooling the body only results in a few degrees of cooling of the CNS. This may be due to protective mechanisms in the hypothalamus of the brain, or due to difficulty in heat/cold exchange between the blood and the brain.
With the new technologies now available, it is time for a new approach to controlling the temperature of the CNS as well as administering medications to the CNS directly in a continuous fashion.